Its surface is rough, slightly glossy, thick, and cracked, with a thin, black hypothallus delineating its borders.

The ascomata are lirelline in form, measuring 8–13 mm in length and bearing a colour similar to the thallus.

The ascospores consistently have 3 transverse septa, are ellipsoidal, and typically measure 8–16 by 3–4 μm, with a 1–2 μm-thick halo.

[2] Fissurina longiramea does not react to any of the standard chemical spot tests, and does not appear to contain lichen products.

In terms of ascomatal structure, the species resembles Fissurina dumastii and F. subnitidula, but is distinguished by its larger lirellae (8–13 mm long).